1. Field of the Invention
This invention relates to a high sensitivity seismograph with an alarm system and particularly, to a small sized seismograph.
2. Description of the Prior Art
The conventional pendulum seismograph is provided a coil attached to the pendulum and a sensitive galvanometer connected to the coil. Motion of the coil in a magnetic field induces an electromotive force which activates the galvanometer and causes its movement. A mirror on the galvanometer deflects a light beam so as to produce record on photographic paper of seismic events. However, the conventional pendulum seismograph cannot measure simultaneously both the left-right motions and the up-down motions of the ground. Furthermore, in order to obtain sufficient magnification, it is difficult to reduce the size of the conventional seismograph significantly, thus, it is very inconvenient for transportation. In addition, conventional seismographs have not been provided with an alarm system, therefore, they cannot give out an early alarming signal before a serious earthquake occurs.
After considerable research work and experiments, it was discovered by the inventor that there are a series of ground motions which last for 2-3 minutes before a big earthquake. If people can make good use of the 2-3 minutes and take important steps, i.e., extinguishing the lights, cutting off electricity sources, getting out of high buildings, the damage brought forth by the earthquake will be reduced on a large scale. Furthermore, in an earthquake a speedy train is apt to leave the rail in a turn when there is a slight ground motion. If a seismograph of the present invention is placed along the rail, the locomotive engineer can slow down the train after he becomes aware of the alarm signal. In places like airports, dams, and the down stream areas of a dam, the damage caused by an earthquake will be reduced substantially if an auto-alarm seismograph has been placed in such a location.